Trail edge buckling sheet buffering system

Abstract

In a copier or printer producing a sequential stream of sheets with limited time therebetween, and with compiling and finishing of those output sheets on-line while subsequent sheets are being printed, a non-slip sheet feeder normally feeding copy sheets downstream to the compiler is selectably intermittently temporarily stopped holding the lead edge area of the first copy sheet for the next set to be finished so that continued feeding of the trail end of the same sheet by a relatively closely spaced upstream feeder buckles that sheet into a buckle chamber assisted by a buckle inducing arcuate baffle extending from the other side of the sheet path. The next printed sheet is fed normally while the buckled first sheet is positively held out of its way. When the second sheet reaches the downstream feeder, it restarts to positively feed both sheets downstream to the compiler, together, but overlapped by a preset amount for registration stacking. A substantial increase is provided in the time for the preceding copy sheets to be operated on in the compiler. A plural sheet collection point may also be provided by this sheet buffering system.

What is claimed is: 
     
       1. For a reproduction apparatus feeding a sequential stream of printed copy sheets into a normal sheet path with a limited space and time therebetween, a sheet buffering system comprising: a non-slip downstream sheet feeding nip normally feeding copy sheets downstream towards a sheet output in said normal sheet path;   said downstream sheet feeding nip being selectably intermittently temporarily stopped with a lead edge of a first copy sheet therein;   a sheet buckle chamber upstream of said downstream sheet feeding nip extending away from said normal sheet path;   a non-slip upstream sheet feeding nip positioned sufficiently closely to said downstream nip along said normal sheet path to simultaneously feed said first sheet in said upstream nip while a lead edge of the same sheet is in said downstream nip to drive the trail end of said first copy sheet into said buckle chamber when said downstream nip is so temporarily stopped, and to then feed a second copy sheet with said upstream nip in said normal sheet path past said first copy sheet in said buckle chamber to said downstream nip;   buckle-inducing sheet baffling in said normal sheet path between said upstream and downstream feeding nips; and   said downstream nip then being automatically restarted upon said feeding of said second copy sheet thereto by said upstream nip to feed said first copy sheet from said buckle chamber in coordination with the feeding of said second copy sheet, so that both said first and second copy sheets are fed downstream by said downstream nip.   
     
     
       2. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said normal sheet path is a sheet output path of said reproduction apparatus, and said reproduction apparatus is provided with a compiler/finisher fed by said output path and said downstream nip for repeatedly sequentially stacking said copy sheets in said compiler/finisher for compiling with edge registration and finishing of said stream of copy sheets into plural collated finished sets on-line as subsequent said copy sheets are being printed and outputted by said sheet output path of said reproduction apparatus, wherein said downstream feeding nip is intermittently temporarily stopped and restarted in coordination with the operation of said compiler/finisher on preceding copy sheets, and wherein said downstream sheet feeding nip is restarted to feed both said first and second sheets together downstream to said compiler/finisher with a substantial increase in the time between the feeding out of said first copy sheet by said downstream sheet feeding nip and preceding copy sheets so fed in said compiler/finisher. 
     
     
       3. The sheet buffering system for a sequential stream of printed copy sheets of wherein said first sheet is lapping said second sheet as they are so fed to said compiler/finisher by said downstream sheet feeding nip, by leading said second sheet at the edges of said first and second sheets which are being edge registered in said compiler/finisher. 
     
     
       4. The sheet buffering system for a sequential stream of printed copy sheets of wherein said normal sheet path is substantially planar and the trailing end of said first sheet is maintained substantially out of said planar normal sheet path in said buckle chamber as a subsequent sheet is fed downstream in said normal sheet path by said upstream nip. 
     
     
       5. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said first sheet is overlying said second sheet as they are fed out by said downstream sheet feeding nip, with the leading edge of the overlying said first sheet extending out ahead of the underlying said second sheet. 
     
     
       6. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein the normal printing order of said first and second sheets is reversed. 
     
     
       7. The sheet buffering system for a sequential stream of printed copy sheets of claim 6, wherein said sheet buckle chamber extends above said normal sheet path. 
     
     
       8. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said sheets are fed by said downstream sheet feeding nip to a compiler tray with edge registration with said first sheet slightly shingled relative to said second sheet for edge registration in said compiler tray. 
     
     
       9. The sheet buffering system for a sequential stream of printed copy sheets of claim 8, wherein the trailing edge of said second sheet fed into said compiler tray by said downstream nip for uphill compiling is underlying said first sheet and following the trailing edge of said first sheet. 
     
     
       10. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said sheet buffering system provides a plural sheet stopping and collection point in said buckle chamber for stopping and collecting plural said copy sheets fed from upstream thereof rather than feeding said plural sheets further downstream in the normal sheet path. 
     
     
       11. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said am nip comprises a rotating upstream sheet feeder, and wherein the trail ends of buckled copy sheets are stripped off of said upstream sheet feeder by a mating baffle, which mating baffle then holds said trail end away from said upstream sheet feeding nip. 
     
     
       12. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said sheet buckle chamber extends above said normal sheet path. 
     
     
       13. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said sheet buckle chamber extends below said normal sheet path. 
     
     
       14. The sheet buffering system for a sequential stream of printed copy sheets of claim 1, wherein said upstream feeding nip is adopted to engage and drive said trail end of the first sheet into said buckle chamber.